Long chain free fatty acids (LCFA) are hydrophobic molecules that play critical metabolic, structural and messenger roles within the cell. Because of their limited aqueous solubility, there should exist mechanisms for the facilitation and regulation of LCFA movement within cells, but such molecular mechanisms remain to be elucidated. The yeast Saccharomyces cerevisiae is a simple eukaryotic system for analysis of the molecular nature of cellular LCFA transport because it provides the feasibility of straightforward genetic manipulation. A range of biochemical, cell biological and genetic techniques will be employed toward understanding the molecular nature of LCFA transport and its regulation. A panel of yeast mutants unable to utilize the LCFA oleate as a carbon source has been isolated, and initial secondary screening has led to the identification of strains possessing characteristics consistent with defects in LCFA transport and/or its regulation. A gene has been cloned by complementation of one of these mutants (fat21). The specific aims to be pursued are: [1] to further examine the fat21 mutant and the role of its complementing gene in LCFA utilization, [2] to isolate and characterize additional yeast mutants in LCFA transport and/or its regulation, and [3] to utilize these mutants to identify and characterize yeast genes and mammalian homologues involved in LCFA transport and/or its regulation. It is expected that progress toward these aims will provide vital tools for the elucidation of the molecular mechanisms and regulation of cellular LCFA transport in eukaryotes, and, ultimately, the investigation of the role of LCFA transport in conditions such as cancer, obesity and cardiovascular disease.